The increasing demand for telecommunications has promoted standardization of high-speed optical transmission methods. For example, ITU-T (International Telecommunication Union Telecommunication Standardization Sector) Recommendation G.709 defines technology for an Optical Transport Network (OTN) of approximately 2.5 to 100 Gbps as disclosed in International Telecommunication Union, “Interfaces for the Optical Transport Network (OTN)”, ITU-T Recommendation G.709/Y.1331, 2009-12.
The optical transmission over the OTN multiplexes optical signals, each accommodating a client signal, by Wavelength Division Multiplexing (WDM), enabling high-capacity transmission. Examples of the client signal accommodated in an optical signal include a Synchronous Digital Hierarchy (SDH) frame, a Synchronous Optical NET (SONET) frame, and an Ethernet (registered trademark) frame.
The frame of the optical signal transmitted over the OTN is called an Optical channel Transport Unit (OTU) frame, and has an overhead, which is control information, a payload containing the client signal, and a Forward Error Correction (EFC), which is an error-correction code. The OTU frame is distributed to, for example, 20 logical lanes and transmitted. At this time, the OTU frame is divided into 16-byte blocks where the overhead, the payload, and the FEC are not distinguished. The blocks are sequentially distributed to the lanes, and transmitted by individual carrier waves of the lanes.